﻿using System;
using System.Collections.Generic;
using System.IO;
using System.Net.Sockets;
using System.Text;
using Microsoft.Extensions.Logging;
using Polly;
using Polly.Retry;
using RabbitMQ.Client;
using RabbitMQ.Client.Events;
using RabbitMQ.Client.Exceptions;

namespace Ray.EventBus.RabbitMQ
{
    /// <summary>
    /// 默认的RabbitMQ持续连接类
    /// </summary>
    public class DefaultRabbitMQPersistentConnection : IRabbitMQPersistentConnection
    {
        IConnection _connection;

        private readonly IConnectionFactory _connectionFactory;
        private readonly ILogger<DefaultRabbitMQPersistentConnection> _logger;
        private readonly int _retryCount;
        bool _disposed;
        object sync_root = new object();

        public DefaultRabbitMQPersistentConnection(
            IConnectionFactory connectionFactory,
            ILogger<DefaultRabbitMQPersistentConnection> logger,
            int retryCount = 5
            )
        {
            _connectionFactory = connectionFactory ?? throw new ArgumentNullException(nameof(connectionFactory));
            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
            _retryCount = retryCount;
        }

        public bool IsConnected => _connection != null
                                   && _connection.IsOpen
                                   && !_disposed;

        public IModel CreateModel()
        {
            if (!IsConnected)
            {
                throw new InvalidOperationException("No RabbitMQ connections are available to perform this action");
            }

            return _connection.CreateModel();
        }

        public bool TryConnect()
        {
            _logger.LogInformation("RabbitMQ Client is trying to connect");

            lock (sync_root)
            {
                //设置重试策略
                var policy = RetryPolicy.Handle<SocketException>()
                    .Or<BrokerUnreachableException>()
                    .WaitAndRetry(_retryCount,
                        retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)),
                        (ex, time) =>
                        {
                            _logger.LogWarning(ex,
                                "RabbitMQ Client could not connect after {TimeOut}s ({ExceptionMessage})",
                                $"{time.TotalSeconds:n1}", ex.Message);
                        }
                    );

                policy.Execute(() =>
                {
                    _connection = _connectionFactory
                          .CreateConnection();
                });

                if (IsConnected)
                {
                    _connection.ConnectionShutdown += OnConnectionShutdown;
                    _connection.CallbackException += OnCallbackException;
                    _connection.ConnectionBlocked += OnConnectionBlocked;

                    _logger.LogInformation("RabbitMQ Client acquired a persistent connection to '{HostName}' and is subscribed to failure events", _connection.Endpoint.HostName);

                    return true;
                }
                else
                {
                    _logger.LogCritical("FATAL ERROR: RabbitMQ connections could not be created and opened");

                    return false;
                }
            }
        }

        #region 连接异常时触发事件
        /// <summary>
        /// 连接阻塞触发
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void OnConnectionBlocked(object sender, ConnectionBlockedEventArgs e)
        {
            if (_disposed) return;

            _logger.LogWarning("A RabbitMQ connection is shutdown. Trying to re-connect...");

            TryConnect();
        }

        /// <summary>
        /// 回调异常触发
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void OnCallbackException(object sender, CallbackExceptionEventArgs e)
        {
            if (_disposed) return;

            _logger.LogWarning("A RabbitMQ connection throw exception. Trying to re-connect...");

            TryConnect();
        }

        /// <summary>
        /// 连接中断触发
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="reason"></param>
        void OnConnectionShutdown(object sender, ShutdownEventArgs reason)
        {
            if (_disposed) return;

            _logger.LogWarning("A RabbitMQ connection is on shutdown. Trying to re-connect...");

            TryConnect();
        }
        #endregion

        public void Dispose()
        {
            if (_disposed) return;

            _disposed = true;

            try
            {
                _connection.Dispose();
            }
            catch (IOException ex)
            {
                _logger.LogCritical(ex.ToString());
            }
        }
    }
}
